Abstract The Southern Helanshan Tectonic Belt (SHTB) is surrounded by the Alxa Massif, the Ordos Basin and the Tibetan Plateau, and its Phanerozoic structures records crucial Phanerozoic deformation characteristics for studying the multi-phased intracontinental deformation processes among these neighboring units. Combined with regional geology, our structural analysis reveals that the SHTB has experienced five phases of shortening deformation during the Phanerozoic. The first phase (D1) is represented by E-W-trending overturned folds in the Cambrian and Ordovician strata. These folds resulted from two episodes of N-S shortening during the Late Cambrian-Early Ordovician and Late Ordovician-Early Devonian respectively, which were attributed to the closure of the Qilian ocean. The second phase (D2) is characterized by E-W-trending open folds involving the Upper Devonian strata, which was the products of N-S shortening caused by the assembly of the Qilian ocean and the North China Craton (NCC) at the end of Devonian. The third phase (D3) is indicated by some WNW-trending Jura-type folds in the Carboniferous strata, formed by NNE-SSW shortening during the Late Triassic-Early Jurassic related to the collision between the NCC and the South China Block. The fourth phase (D4) is inferred by NNE-trending shortening structures in the Jurassic and its underlying strata, generated by WNW-ESE shortening in the Late Jurassic echoing the Paleo-Pacific subduction. The fifth stage (D5) is characterized by the NE-SW shortening in the Late Miocene, leading to the formation of many NW-SE striking thrust faults in the Miocene and its underlying strata, because the outward expansion of the Tibetan Plateau.

中文翻译：

---

华北贺兰山构造带南部多期变形

摘要 贺兰山南部构造带（SHTB）被阿拉善地块、鄂尔多斯盆地和青藏高原所环绕，其显生宙构造记录了重要的显生宙变形特征，为研究这些相邻单元之间的多期陆内变形过程提供了重要依据。结合区域地质，我们的构造分析表明，SHTB在显生宙期间经历了五个缩短变形阶段。第一阶段（D1）以寒武系和奥陶系地层东西向的翻转褶皱为代表。这些褶皱分别是由晚寒武世-早奥陶世和晚奥陶世-早泥盆世期间两次NS缩短引起的，这归因于祁连洋的闭合。第二阶段（D2）以东西向开放褶皱为特征，涉及上泥盆统地层，是泥盆纪末祁连洋与华北克拉通（NCC）组装引起的南北向缩短的产物。第三阶段（D3）由石炭纪地层的一些WNW向侏罗型褶皱指示，由晚三叠世-早侏罗世NNE-SSW缩短形成，与NCC与华南地块碰撞有关。第四阶段（D4）是由侏罗纪及其下伏地层中的 NNE 向缩短结构推断的，由晚侏罗世的 WNW-ESE 缩短产生，与古太平洋俯冲相呼应。第五阶段（D5）以晚中新世的 NE-SW 缩短为特征，